[WIP] flamenco, vm: add bpf loader serialization test fixtures

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Adds a set of fixtures and a unit test fixture runner for vm input serialization, generated by running the input through the Agave vm input serializers. Compares the output buffer, the vm regions and the region metadata. Includes coverage of stricter_abi_and_runtime_constraints and account_data_direct_mapping.

Adjusted some of the serialization code to make it more amenable for unit testing, removing the dependency on fd_runtime_t.

[topointon-jump]

This pr depends on, and adds tests for, https://github.com/firedancer-io/firedancer/pull/7389. Needs to be rebased when 7389 is merged.

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Performance Measurements ⏳

Suite	Baseline	New	Change
backtest mainnet-368528500-perf per slot	0.0733 s	0.074339 s	1.417% ✅
backtest mainnet-368528500-perf snapshot load	3.796 s	3.144 s	-17.176% ✅
backtest mainnet-368528500-perf total elapsed	73.300332 s	74.339282 s	1.417% ✅
firedancer mem usage with mainnet.toml	1013.23 GiB	1013.23 GiB	0.000% ✅

[github-actions[bot]]

Performance Measurements ⏳

Suite	Baseline	New	Change
backtest mainnet-368528500-perf per slot	0.073295 s	0.07316 s	-0.184% ✅
backtest mainnet-368528500-perf snapshot load	3.785 s	3.208 s	-15.244% ✅
backtest mainnet-368528500-perf total elapsed	73.294634 s	73.159935 s	-0.184% ✅
firedancer mem usage with mainnet.toml	1013.23 GiB	1013.23 GiB	0.000% ✅

[github-actions[bot]]

Performance Measurements ⏳

Suite	Baseline	New	Change
backtest mainnet-368528500-perf per slot	0.076924 s	0.076404 s	-0.676% ✅
backtest mainnet-368528500-perf snapshot load	4.846 s	3.059 s	-36.876% ✅
backtest mainnet-368528500-perf total elapsed	76.924404 s	76.404374 s	-0.676% ✅
firedancer mem usage with mainnet.toml	1013.23 GiB	1013.23 GiB	0.000% ✅